1. Field of the Invention
The present invention relates to inspection equipment which is used in the process of manufacturing semiconductor devices. More particularly, the present invention relates to a stage assembly of a microscope used to examine wafers during the manufacture of a semiconductor device.
2. Description of the Related Art
The manufacturing yield of semiconductor devices can be reduced by process defects, material defects and various contaminants. Particles in the working environment are typical of such contaminants. In particular, particle defects are becoming a more serious problem as semiconductor devices become smaller in line with the demand for higher integration. Accordingly, the degree to which the cleanliness of the working environment is maintained must be improved. Therefore, processing equipment is continuously being redesigned to counter the problems of particle contamination of the working environment. However, such an effort has not yet been applied to secondary equipment which is used in connection with the manufacturing process but is operated away from the working environment. An example of such secondary equipment is the microscope. The introduction of particles into the working environment from such equipment is a problem which can be easily overlooked.
FIGS. 1 and 2 show a stage assembly of a conventional microscope. Referring to FIG. 1, the microscope generally comprises an upper end 52 including an objective lens(es) 56, and a lower end 54 including a stage assembly 50 and a focusing knob 58. In FIG. 1, reference numerals 62, 63 denote gears for moving the stage 60 of the stage assembly 50 along X and Y axes. The stage 60 supports an object to be examined, such as a wafer. Reference numeral 64 denotes a stage control column. Reference numeral 66 denotes a knob for controlling the movement of the stage 60 along the X and Y axes.
FIG. 2 is an enlarged side view of the stage assembly 50. The stage 60 is moved along the X and Y axes by an X-axis rack 84, a Y-axis rack 82, an X-axis drive pinion 62 and a Y-axis drive pinion 63 mounted on the stage control column 64. The control knob 66 includes a Y-axis control knob 72 and an X-axis control knob 74 mounted on the end of the stage control column 64. A separation plate 76 is interposed between the X-axis drive pinion 62 and the Y-axis drive pinion 63. A first fixing screw 78 in the separation plate 76 is connected to the stage 60. Therefore, the stage 60 can be moved along the X and Y axes in order to examine different parts of an object supported thereon. An operator wearing gloves moves the stage 60 along the X and Y axes by rotating the X- and Y-axis control knobs 74 and 72 provided on the end of the stage block control column 64.
However, the above-mentioned conventional technology has a problem in that particles such, as metal or TEFLON (a heat resistant, scratch resistant coating) fragments, come off the mating surfaces of the X- and Y-axis racks 62 and 63, and the X- and Y-axis drive pinions 84 and 82. The particles adhere to the hands of the worker, and thereby migrate into the working environment. TABLE 1 shows the results of measuring the metal fragments which had accumulated beneath the stage during a day.
TABLE 1 ______________________________________ Particle Count ______________________________________ size of 0.07 0.10 0.15 0.20 0.30 0.50 0.70 1.00 particles (.mu.m) number of 32 32 29 25 20 10 7 6 particles (N) ______________________________________
It can be confirmed that particles in the quantities shown in the TABLE 1 cause various defects in the semiconductor devices, thus reducing the yield of the manufacturing process.